Recent advancements in micro-flow technologies and a drive toward more efficient, greener and safer processes have led to a renaissance in flow-chemistry for pharmaceutical production. In this work, we demonstrate the use of a stabilized Pd nanoparticle-organic-silica catalyst to selectively catalyze the hydrogenation of N-4-nitrophenyl nicotinamide, a functionalized active pharmaceutical ingredient (API) surrogate. Extensive catalyst and reactor characterization is provided to establish an in-depth understanding of the unique multiphase dynamics within the micro-packed bed reactor, including the identification of a large liquid holdup (74-84%), rapid multiphase mass transfer (k(m)a > 1 s(-1)), and liquid residence time distributions. A kinetic analysis has revealed that the surface catalyzed hydrogenation progresses through a condensation mechanism whereby an azo dimer intermediate is formed and rapidly consumed. Finally, a parametric study was performed at various pressures, temperatures, residence times and flow regimes to achieve quantitative chemoselective conversion of the nitroarene to the corresponding primary amine.

• Massachusetts Institute of Technology (MIT) (MIT)
• University of Cambridge
• Novartis Pharma AG

• API

1. Active pharmaceutical ingredient
2. API
3. chemoselective conversion
4. micro-packed bed reactor
5. N-4-nitrophenyl nicotinamide
6. nitroarene 
7. Research Article